mirror of
https://github.com/git/git
synced 2024-08-27 19:49:21 +00:00
![Luck, Tony](/assets/img/avatar_default.png)
Update documentation to warn users not to create noise in then Linux history by creating pointless "Auto-update from upstream" merge commits. Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Junio C Hamano <junkio@cox.net>
297 lines
8.5 KiB
Plaintext
297 lines
8.5 KiB
Plaintext
Date: Mon, 15 Aug 2005 12:17:41 -0700
|
|
From: tony.luck@intel.com
|
|
Subject: Some tutorial text (was git/cogito workshop/bof at linuxconf au?)
|
|
Abstract: In this article, Tony Luck discusses how he uses GIT
|
|
as a Linux subsystem maintainer.
|
|
|
|
Here's something that I've been putting together on how I'm using
|
|
GIT as a Linux subsystem maintainer.
|
|
|
|
-Tony
|
|
|
|
Last updated w.r.t. GIT 1.1
|
|
|
|
Linux subsystem maintenance using GIT
|
|
-------------------------------------
|
|
|
|
My requirements here are to be able to create two public trees:
|
|
|
|
1) A "test" tree into which patches are initially placed so that they
|
|
can get some exposure when integrated with other ongoing development.
|
|
This tree is available to Andrew for pulling into -mm whenever he wants.
|
|
|
|
2) A "release" tree into which tested patches are moved for final
|
|
sanity checking, and as a vehicle to send them upstream to Linus
|
|
(by sending him a "please pull" request.)
|
|
|
|
Note that the period of time that each patch spends in the "test" tree
|
|
is dependent on the complexity of the change. Since GIT does not support
|
|
cherry picking, it is not practical to simply apply all patches to the
|
|
test tree and then pull to the release tree as that would leave trivial
|
|
patches blocked in the test tree waiting for complex changes to accumulate
|
|
enough test time to graduate.
|
|
|
|
Back in the BitKeeper days I achieved this by creating small forests of
|
|
temporary trees, one tree for each logical grouping of patches, and then
|
|
pulling changes from these trees first to the test tree, and then to the
|
|
release tree. At first I replicated this in GIT, but then I realised
|
|
that I could so this far more efficiently using branches inside a single
|
|
GIT repository.
|
|
|
|
So here is the step-by-step guide how this all works for me.
|
|
|
|
First create your work tree by cloning Linus's public tree:
|
|
|
|
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git work
|
|
|
|
Change directory into the cloned tree you just created
|
|
|
|
$ cd work
|
|
|
|
Set up a remotes file so that you can fetch the latest from Linus' master
|
|
branch into a local branch named "linus":
|
|
|
|
$ cat > .git/remotes/linus
|
|
URL: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
|
|
Pull: master:linus
|
|
^D
|
|
|
|
and create the linus branch:
|
|
|
|
$ git branch linus
|
|
|
|
The "linus" branch will be used to track the upstream kernel. To update it,
|
|
you simply run:
|
|
|
|
$ git fetch linus
|
|
|
|
you can do this frequently (and it should be safe to do so with pending
|
|
work in your tree, but perhaps not if you are in mid-merge).
|
|
|
|
If you need to keep track of other public trees, you can add remote branches
|
|
for them too:
|
|
|
|
$ git branch another
|
|
$ cat > .git/remotes/another
|
|
URL: ... insert URL here ...
|
|
Pull: name-of-branch-in-this-remote-tree:another
|
|
^D
|
|
|
|
and run:
|
|
|
|
$ git fetch another
|
|
|
|
Now create the branches in which you are going to work, these start
|
|
out at the current tip of the linus branch.
|
|
|
|
$ git branch test linus
|
|
$ git branch release linus
|
|
|
|
These can be easily kept up to date by merging from the "linus" branch:
|
|
|
|
$ git checkout test && git merge "Auto-update from upstream" test linus
|
|
$ git checkout release && git merge "Auto-update from upstream" release linus
|
|
|
|
Important note! If you have any local changes in these branches, then
|
|
this merge will create a commit object in the history (with no local
|
|
changes git will simply do a "Fast forward" merge). Many people dislike
|
|
the "noise" that this creates in the Linux history, so you should avoid
|
|
doing this capriciously in the "release" branch, as these noisy commits
|
|
will become part of the permanent history when you ask Linus to pull
|
|
from the release branch.
|
|
|
|
Set up so that you can push upstream to your public tree (you need to
|
|
log-in to the remote system and create an empty tree there before the
|
|
first push).
|
|
|
|
$ cat > .git/remotes/mytree
|
|
URL: master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
|
|
Push: release
|
|
Push: test
|
|
^D
|
|
|
|
and the push both the test and release trees using:
|
|
|
|
$ git push mytree
|
|
|
|
or push just one of the test and release branches using:
|
|
|
|
$ git push mytree test
|
|
or
|
|
$ git push mytree release
|
|
|
|
Now to apply some patches from the community. Think of a short
|
|
snappy name for a branch to hold this patch (or related group of
|
|
patches), and create a new branch from the current tip of the
|
|
linus branch:
|
|
|
|
$ git checkout -b speed-up-spinlocks linus
|
|
|
|
Now you apply the patch(es), run some tests, and commit the change(s). If
|
|
the patch is a multi-part series, then you should apply each as a separate
|
|
commit to this branch.
|
|
|
|
$ ... patch ... test ... commit [ ... patch ... test ... commit ]*
|
|
|
|
When you are happy with the state of this change, you can pull it into the
|
|
"test" branch in preparation to make it public:
|
|
|
|
$ git checkout test && git merge "Pull speed-up-spinlock changes" test speed-up-spinlocks
|
|
|
|
It is unlikely that you would have any conflicts here ... but you might if you
|
|
spent a while on this step and had also pulled new versions from upstream.
|
|
|
|
Some time later when enough time has passed and testing done, you can pull the
|
|
same branch into the "release" tree ready to go upstream. This is where you
|
|
see the value of keeping each patch (or patch series) in its own branch. It
|
|
means that the patches can be moved into the "release" tree in any order.
|
|
|
|
$ git checkout release && git merge "Pull speed-up-spinlock changes" release speed-up-spinlocks
|
|
|
|
After a while, you will have a number of branches, and despite the
|
|
well chosen names you picked for each of them, you may forget what
|
|
they are for, or what status they are in. To get a reminder of what
|
|
changes are in a specific branch, use:
|
|
|
|
$ git-whatchanged branchname ^linus | git-shortlog
|
|
|
|
To see whether it has already been merged into the test or release branches
|
|
use:
|
|
|
|
$ git-rev-list branchname ^test
|
|
or
|
|
$ git-rev-list branchname ^release
|
|
|
|
[If this branch has not yet been merged you will see a set of SHA1 values
|
|
for the commits, if it has been merged, then there will be no output]
|
|
|
|
Once a patch completes the great cycle (moving from test to release, then
|
|
pulled by Linus, and finally coming back into your local "linus" branch)
|
|
the branch for this change is no longer needed. You detect this when the
|
|
output from:
|
|
|
|
$ git-rev-list branchname ^linus
|
|
|
|
is empty. At this point the branch can be deleted:
|
|
|
|
$ git branch -d branchname
|
|
|
|
Some changes are so trivial that it is not necessary to create a separate
|
|
branch and then merge into each of the test and release branches. For
|
|
these changes, just apply directly to the "release" branch, and then
|
|
merge that into the "test" branch.
|
|
|
|
To create diffstat and shortlog summaries of changes to include in a "please
|
|
pull" request to Linus you can use:
|
|
|
|
$ git-whatchanged -p release ^linus | diffstat -p1
|
|
and
|
|
$ git-whatchanged release ^linus | git-shortlog
|
|
|
|
|
|
Here are some of the scripts that I use to simplify all this even further.
|
|
|
|
==== update script ====
|
|
# Update a branch in my GIT tree. If the branch to be updated
|
|
# is "linus", then pull from kernel.org. Otherwise merge local
|
|
# linus branch into test|release branch
|
|
|
|
case "$1" in
|
|
test|release)
|
|
git checkout $1 && git merge "Auto-update from upstream" $1 linus
|
|
;;
|
|
linus)
|
|
before=$(cat .git/refs/heads/linus)
|
|
git fetch linus
|
|
after=$(cat .git/refs/heads/linus)
|
|
if [ $before != $after ]
|
|
then
|
|
git-whatchanged $after ^$before | git-shortlog
|
|
fi
|
|
;;
|
|
*)
|
|
echo "Usage: $0 linus|test|release" 1>&2
|
|
exit 1
|
|
;;
|
|
esac
|
|
|
|
==== merge script ====
|
|
# Merge a branch into either the test or release branch
|
|
|
|
pname=$0
|
|
|
|
usage()
|
|
{
|
|
echo "Usage: $pname branch test|release" 1>&2
|
|
exit 1
|
|
}
|
|
|
|
if [ ! -f .git/refs/heads/"$1" ]
|
|
then
|
|
echo "Can't see branch <$1>" 1>&2
|
|
usage
|
|
fi
|
|
|
|
case "$2" in
|
|
test|release)
|
|
if [ $(git-rev-list $1 ^$2 | wc -c) -eq 0 ]
|
|
then
|
|
echo $1 already merged into $2 1>&2
|
|
exit 1
|
|
fi
|
|
git checkout $2 && git merge "Pull $1 into $2 branch" $2 $1
|
|
;;
|
|
*)
|
|
usage
|
|
;;
|
|
esac
|
|
|
|
==== status script ====
|
|
# report on status of my ia64 GIT tree
|
|
|
|
gb=$(tput setab 2)
|
|
rb=$(tput setab 1)
|
|
restore=$(tput setab 9)
|
|
|
|
if [ `git-rev-list release ^test | wc -c` -gt 0 ]
|
|
then
|
|
echo $rb Warning: commits in release that are not in test $restore
|
|
git-whatchanged release ^test
|
|
fi
|
|
|
|
for branch in `ls .git/refs/heads`
|
|
do
|
|
if [ $branch = linus -o $branch = test -o $branch = release ]
|
|
then
|
|
continue
|
|
fi
|
|
|
|
echo -n $gb ======= $branch ====== $restore " "
|
|
status=
|
|
for ref in test release linus
|
|
do
|
|
if [ `git-rev-list $branch ^$ref | wc -c` -gt 0 ]
|
|
then
|
|
status=$status${ref:0:1}
|
|
fi
|
|
done
|
|
case $status in
|
|
trl)
|
|
echo $rb Need to pull into test $restore
|
|
;;
|
|
rl)
|
|
echo "In test"
|
|
;;
|
|
l)
|
|
echo "Waiting for linus"
|
|
;;
|
|
"")
|
|
echo $rb All done $restore
|
|
;;
|
|
*)
|
|
echo $rb "<$status>" $restore
|
|
;;
|
|
esac
|
|
git-whatchanged $branch ^linus | git-shortlog
|
|
done
|